Lignin reinforced rubber and method of making same



Aug. 26, 1952 A. POLLAK 2,598,537

' LIGNIN REINFORCED RUBBER AND METHOD OF MAKING SAME Filed July 12, 1947:s Sheets-Sheet 2 TEAR RESISTANCES OF uaum AND CARBON BLACKS EQUALI/QLI/ME LOAD/NGS-GR-S 600 /ue/v//v 40o EPC //\\HMF 3 51W 200 SHORE ,"4"HARDNLSS L 'GN/N loo so 5% 5/1. SRF

pc v HMF I HMA A 4o 0 so 75. I00

VOLUME 0/" PIG/VENT PEI? I00 PARTS OF 619-5 85 PER SQUARE INCH 2000INVENTOR 50 40 0 men/Me Ava/m L/GN/N, 4 55 P52 m0 155 was a l l I BY W-0 m 20 so CARBON BLACK,B$ PER /0o. .55 GR-S ATToRN-EY5 Au 26, 1952POLLAK 2,608,537

LIGNIN REINFORCED RUBBER AND METHOD OF MAKING SAME Filed July12, 1947 sSheets-Shee t s PROPERT Es OF GR-S AT BY I ATTORNEYS Patented Aug. 26,1952 LIGNI N REINFORCED RUBBER AND METHOD OF MAKING SAME.

Arthur Pollak, Charleston, S. (3., assignor to West Virginia Pulp andPaper Company, New York, N. Y., a corporation of Delaware ApplicationJuly 12, 1947, Serial No. 760,634

.53 Claims. 1 The present invention relates to improvements in rubbercompounding. 1 One principal reason for compounding irubber', eithernatural orsynthetic, is to reduce. its elasticity and increase itsstrength, such result being obtained when withthe rubber is incorporatedin homogeneous admixture fillersv such as carbon black and, to a lesserdegree, other finely divided pigments. The reason for the superiority ofcarbon black is considered to reside principally in the extreme degreeof subdivisionof itsparticles, the average particle size being in therange 0.01 to 0.10 micron (1 micron equals of a millimeter). Because ofthe superiority of carbon blackas a reinforcing agent, strength mustusually be sacrificed whena white or light colored stock is desired,since the white pigments, as for example zinc oxide, clay and the like,do not have as great a reinforcing action as carbon. As ordinarilypractised, the incorporation of the carbon black or other substance,termed a reinforcing agent because of its beneficial action, is precededby a mastication and softening of the rubber in an appropriate type ofmill, e. g, a Banbury mixer, or a two-roll mill, this operation beingtermed a breakdown. When the breakdown has progressed to a certainpoint, plasticizers and softeners are added, followed, at theappropriate time with the addition of fillers, and then other chemicalssuch as accelerators, antioxidants, and vulcanizing agents, the millingbeing continued to disperse the f'coinpounding ingredients inthe rubber.Iiithe attempt to secure a more perfect dis tribution of reinforcingagent and rubben'it has been proposed to coprecipitate the rubber fromits dispersed or latex state with thefiller'which has previously beenmade into an aqueous suspension and mixed with the latex, thesimultaneous precipitation of the two principalingredients being broughtabout by the addition of an appropriate precipitating agent. The usualrubber chemicals are then milled into the dried precipitate or crumb.

Most rubber including natural rubber and the largest proportion ofsynthetic rubbers occurs as latex. The principal synthetic rubbers arethe copolymer of butadiene and styrene (GR-S) the copolymer of butadieneand acrylonitrile (GR-A) and thepolymerof chlorobutadiene (GR-M) I havenow discovered that by coprecipitating natural or synthetic rubber inthe latex form with lignin as a reinforcing agent and filler, the.rlesulting crumb when dried yields compounds having unique and valuableproperties. Because of the high degree of dispersion of the lignin inthe rubber, little milling time is needed for completing the breakdown.Generally ithas been observed that where crude rubber required 20minutes for breakdown, the lignin latex coprecipitate required only 2 to4 minutes. In addition the time required fordispersing pigment, another20 minutes, is also saved. In general the compounds so produced havetensile strengths and tear resistances which at lower loadings arecomparable with those obtainedusing carbon blacks, while havingproperties not possessed by rubbers containing carbon blacks as the solereinforcing agent, such as lightness of color, decreased specificgravity, increased elongation and decreased time of breakdown; at higherloadings the lignin reinforced compounds are characterized by highertensile strengths and higher tear resistances than the correspondingcarbon black reinforced compounds.

Among the rubber-reinforcing agents, the lignin referred to herein isunique in that it is soluble in aqueous alkali, such solutions beingcompatible with the latex emulsions in all proportions. Furthermore, itis possible to precipitate both the lignin and the rubber and otherpigment from the mixture by use of acids in the same pH range as iscommonly used in coagulating or precipitating latex alone, suchprecipitates containing the lignin so well dispersed in the rubber as toafford excellent reinforcing action upon compounding and curing.

In the drawing, Figures -1 and 2 show curves having a common horizontalaxis designating volumes of lignin. per 100 parts (by weight) GR-S, andindicating respectively tensile strength (Fig. l) and elongation atbreak and set after break (Fig. 2) for GR-S reinforced with lignin inaccordance with the present invention, and with three of the commoncarbon blacks, namely Easy Processing Channel Black (EPC), High ModulusFurnace Black (HMF) and Semi- Reinforcing Furnace Black (SRF). In.Figure 2, the set after break is given forlignin only.

Figure 3 shows similar curves in which the tear resistance of ligninreinforced CTR-S is compared with that of carbon black reinforced GR-Sof equal volume loadings; in Figure 3A are curves having the samehorizontal axis as Figure 3 and in which Shore hardness of ligninreinforced GR-S and carbon blackreinforced GR-S are compared for equalloadings.

Figure 4 is a curve showing tensile strength of GR-S-lignin-carbon blackmixtures.

and that the resulting dispersions are compatible with latex emulsions.Thus, the so dispersed is therefore a feature of my invention to carryOut'the coprecipitating step in a manner which A still further examplein which the lignin to carbon ratio is low:

Mix 2.5 pounds of lignin and 74 pounds of water Then add 1.0 pound of50% caustic soda And 22.5 pounds of carbon black.

.In the ,usepf, ,coprecipitated ligninas a reinforcing agent for rubber,difliculty may be experienced in that a precipitate or crumb is obtainedwhich is not easily filterable and washable. It

. overcomes this difliculty.

carbon black or pigment may bemixed with latex and" the mixture thencopre'cipitated withlasu-itable precipitating agent,whereupon,the-carbon: black or pigment, the lignin, and the rubber areall precipitated together.

Prior to my discovery the dispersing agents available for carbon .blackpresented serious problems. .Thus somefojf them proved effectivedispersants for the pigment. but couldnot be inactivated duringcoprecipitation so that the-co :figulurn' proved difiicult to filter andthe washing losses of eithe'r nibber'or pigment or both were very'serioush Qther' dispersing agents proved incompatible with the latex.so that coagulation set inbefore adequate mixing was attained. Mostoftl je dispersing agentswere' also objectionable because their residues in the c oprecipitates exercised aYdeleterious effect on the'res'ulting' jrubber. flhese 'various objections, howevenare overjcomeby the use of lig'nin in thatit coprecipitates withgthe pigmentfromcompatible dispersions and "is inactivated and converted to. areinforcing agent; The carbon black may be dispersed in Water by firstmixing'lignin' and carbon blackin 'their dry states-and thenv addingalkali solutions to the mixture; or, an alkaline ligninv solution may.be 'stirredintoa slurry of carbo'n black.

Another procedure is fto rnix the'dryfcarbon into an alkalinelignin'solution. Ineither event, the resulting dispersions maybe dilutedwith water as desired. The amount ofligninused beyond the quantityneeded ,asa dispersing agent will depend L 'on .the proportions oflignin desired in the.rub- 'ber. Sincethe lig nin coprecipitatesiwiththe rubfberfithe use of relatively large amounts thereof does.notincrease the loss of carbon ,or rubber .d -lringthe washing','as is.the case with other wetting orldispersing agents. An example ofdispersing carbon black in an aqueous alkaline lignin solution is asfollows:

'Mix;12.5 pounds of lignin i i And.'l'2.5 pounds of carbon black :Add 70pounds of water Andi-then 5 pounds of-50%v caustic soda.

, resulting pounds of the mixture contains 12.5% lignin inthe form ofsodiumf -lignate, and 1 2.5% or dispersed lc'arbon black, 'or a total of125%- of greinforcing" agents. 'An example of a ligninti-tanium oxiderdispersionv follows Mix-'zopounds'u nm 1 'A nd 5"pounds titaniumdioxide (T102) iTh'en ad'd fi'l'pounds of water I Thenadd 8 po-unds of50% caustic soda.

A. further example, involving calcium carbonate:

Mix 12.5 pounds 'lignin 12.5 poundsoffinely divided precipitated calciumcarbonate." Add 70 pounds water and then 5 pounds of 50% caustic soda. 1i a contained 25% lignate.

lignin.solution. I

My. invention will now be further illustrated by thejollo'vving examplesPreparation- 0f a Tubber-ltgnin coprecipitate or 1 A. solution of ligninwas first made by preparing a slurry of pounds thereof in 65 pounds ofwater and then adding 10 pounds of cans tic soda. The resulting 100'pounds ofsolution ligmn in the-form {of Sodium '26 poundsof GRz-S latexlcopolymerofbut?" diene and styrene) containing anti-oxidants'a'ndgshort fstop' agents-having a rubber content of 33 :pounds: was mixedwith 10 pounds of the "25% :Azi==0.8'%"' sulfurio acid solution wasprepared bypadding 1.8 pounds of B. (77.7%) sulfuric acid -tojl 78pounds of Water. This solution was heated to 194 F. and the'lignin-latex' mixture --s1o.wly added thereto Whileagitating'thoroughly.

The mixture. now containing a-coprecipitate ,ol 50:.parts lignin toparts rubber, was then filtered; in this instance using a lead-filter'press fitted with12" by 12-by 1" frames. -The cake was washed inthe press with 800 pounds of water. Vacuum filterswere also foundsatisfactoryin other experiments. The'washed cake 'or crumb "was. thendried in an air oven at a temperature-of 1160 1 By-so proceedingan-easily-filterable coprecipitate wasobtaine j Compounding-thecoprecim'tate The ,lignin-Glt-S .coprecipitates of various loadings1similarly. prepared were compounded by the followi-ngformula, parts byweight:

'Benzothiazyl disulfide; Copper diethyldithiocarbamatm. 0.6/100 A Acommercial product whclrs rosn softenedwith tur- Dentine.

tested as. follows:

Specimens of such-loadings; cured at 292? lii nin- Tc11s1le T 1b 7i 6 6i th. Resistance Ga s IMF/SW1? --1bs./in. I

fI heaboverecipe and others that follow are, so far as the ingredients,.other than. lignin are concerned, patterned after typical GR-S recipesand" have 'givena satisfactory product. with the customary. processingequipment. Other recipes could be devised by those skilled in the artwhich would be'equally satisfactory. I l

Otherresults are given in the form of the curves of Figs. 1, 2, 3 and 3Ain which the relationships of tensile strength, elongation at break,tear resistance and hardness are all plotted against volumeloadings ofGR-S of both lignin and three of the common carbon blacks. Thecarbonblack data given in Fig. 1 are taken from Bulletin No.. 3ofGodfrey L. Cabot, Inc. In Fig.1 it will be noted that .up to about 37volumes loading, the tensile strength for lignin reinforced GR-S issomewhere between that for Easy. Processing Channel Black and HighModulus Furnace Black. However, at higher loadings, e. g. upto 100volumes, the value for lignin reinforced GRF-S issubstantially greaterthan for the carbon blacks and the value for 100 volumes lignin loadingis approximately that for 25 volumes lignin loading. The tear resistance(Fig. 3) is given in respect of ASTM Die B and the curves for tearresistances are essentially similar to those .for tensile strength. TheShore A hardness of the lignin compounds is somewhat higher though ofsubstantially the same magnitude. 1

(In the rubber trade it is common to refer to reinforcing agents interms of volume. For example,'carbon black having a specific gravity of1.8 has a specific volume of0.56. Lignin, having a specific gravity of1.3 has a specific volume of 0.77. On the other hand it is customary torefer to the rubber component by parts by weight.) w I In Figs. 5 to 12are shown the properties of lignin loaded GR-S asl'compared withloadings with other pigments, Figs. 5 to 8, inclusive, referring to 38.5volume'loadings whereas Figs. 9 to 12 refer to 77 volumes loading, 1.e., volumes of pigment to 100 parts by weight of GR-S. It will be seenfrom these figures that at the higher loadings the lignin has greatertensile strength than the other pigments. tested, has slightly greater.Shore hardness than the carbon blacks and. the calcium silicate, hassubstantially greater: crescent tear resistance than the other pigments,has greater elongation than the carbon blacks taken with a comparativelylow set at break; The differences at 38.5 volumes while similar in mostinstances are not as marked.

Lignin is compatible with other rubber reinforcing. agents, particularlycarbon black, and in Fig. lithe-curve of tensile 'strengthis plotted formixtures of: from parts lignin to 50 parts carbon black, to .50 parts oflignin and 0 parts carbon black, the total loading (by weight)alwaysrbeing ,50 pounds, this loading being chosen becausein general itis recognized that maximum tensilestrengths .occur around such 1 value.It-will be noted that'in the region of parts lignin, 45. parts carbonblack, the curve reaches a .maximum and has ahigher tensile value thanwith no lignin atall. From parts lignin, 40 parts carbon black to 50parts lignin and no carbon black, the curve slopes slightly downward.:The data given in Fig. 4 were obtained by coprecipitating the carbonblack and lignin but comparable results are obtained by firstcoprecipitating the rubber and the lignin and then incorporating thecarbon black by dry milling. However, in the case of some carbon blacks,particularly medium processing channel black and high processing channelblack, the milling operation israttended 5 with some difliculty so thatcoprecipitation of both reinforcing agents and the rubber "is of'substantial' advantage. If desired, :however. theligninmay becoprecipitated with the rubber -at high loading, the product beingtermed a master "batchand then therubber, as for examplaGR-S, added bydry milling to bring the'proporti'onbfthe lignin to that desired in thefinal mixture and then the carbon blachadded by dry milling. This methodlikewise gives substantially ;the same results as given -in,.Fig'.'4.'Referringto Fig. 4 the following compounding recipe was used, the partsby weight: l

Gas f Lignin; Carbon Black (EPC) Zinc oxide .-5 I

Benzothiazyl disulfide i. 1.5 v 1 Copper diethyldithiocarbamate 0.6/lignin, Plasticizer 8 I. r p f f Sulfur 2 Rubbers other than thoseoriginally 'occurring as latices, e. g. Butyl, reclaimedrubberpe tc. mayalso be dry milled into the rubber lignin coprecipitate. Thecompatibility of lignin...with carbon black as a reinforcing agent hasbeen brought out; in the foregoing. f This cornpatibility extends toother -fill'e'rs, with *thejresult that the reinforcing action of ligninis an additive one. This action is shown in the follow-1 ing data: I trE's'rLEsTRE o'rmP; s. 1.

V N0 Half Pigment Vols. Lignin Lignin,

Coated Calcium Carbonate A 38.5 "900 Clay Calcium Silicate d TEARRESISTANCE; LBS./IN..

Pigment Vols. 4 2,

Coil-ted Calcium carbonates"; CalciumSilicate. ;.ii i l.i. .3825

A further advantage arises from the 'facti'that lignin has a lower;density than carbo'n black, i. e.,'1. 3 as'compared with 1'.8'1*.9 'forcarbon blacks In comparison with other fillers such as clay and calciumcarbonate (specific gravity 2.6), 'titanium oxide (sp. /g. '3 i9). *zincoxide (sp./g. 5.6) appreciable :savi ng's weight'may be had by the useof ligninr 'In many applications this is a highly importantconsideration. For example, in a rubber tire tread stock using lignin asaving of 7% in weight results for a formula normally using 50partscarbon black per 100 parts rubber. L

Lignin has a much lower pigmenting power than carbon black, .so'thatwith its use it is possible to produce brightly colored rubber productsber compounding -.plant,ia.master, batch of, ligninloaded-;;rubb.erE-ob,talned by" coprecipitation, as

above amentionects may -be5supplied, the. compounderi.whoothereuponbreaks it-;do.wn and complates the icolhpound-ingwith.additional rubber andcarbon-onsuch; other mix as ,-may;be desired. Theforegoing examples involve GET-,5. The following .i'spanF example ,of.,;coprecipitating. and compounding natural 1' rubber with lignin:

I I v 1 Parts Natural rubberlatex' containing 38.5 solids to" EiYQ'IOO'parts rubber J Lignin'jas sodium lignatettp, ;giv e '50-]parts Qlignin. 1 Zinc oxide 5w Mercaptobenzothiazole 1.

Tetramethylthiuram monosulfideul Stearic acid Antioxidant A-'s'a-mple ofthis compound cured *for five frninutes at 292 F. gave results asfollows:

' Tensile strengthl p. s. 1. "13 9870 Modulus at 300% longation, p-. s.i

Tear resistance, lbs. /in S e iih ngsa lilg'he followiing is a"similar'examplegofgcompounm U ins-gl .s met nitatin -nit i ei r ber A wi h-1 4211- I 1 I g I I, 1. 5 Parts Nitrile rubber latex containing 26molpercent acrylonitrile to give 100. parts rubber.

' Lignin as sodium lignate to give 50 parts In both 101' the exampleslast given the rubber was coprecipitated with the lignin in the samemanner as in the case of the GR-S lignin coprecipitates previouslygiven;

- ,As; expected the: ,tensile; strength and I tear .;re-

sistance-of natural rubber is somewhat hi her I than in ;-the case of;1GB S for-.ethesame loadings (33.5 wolume loading of lignin-being. thesame as ;50 parts by weight) The;:use pfxli nin, wi h other syntheticrubbers, as forgexamplejneoprene (GR-M) is. also advantageous I.When-theso-called wetcrum'b, i.. e.,-the filter cake fromi theoperation of filteringthe lignin rubber coprecipitate, is milled inknown devices -(Plasticat0r, Colloid MilL-Banbury mixer or roller mill)the lignin is caused to undergo ,an 'even furthersubdivision in particlesize due :to the shearing-action which takes-place in the gelled ligninparticles, If desired; advantage may-be taken of this shearing action;by adding I gelled lignin to .the mixture during the milling operation.Lignin in the gelled state is available (51):: from the ligninpreparedfrom :black liquor :-prior. to

drying, -,('2) "by. soaking: ,.0r grinding 1 dried lignin 8 withsufficient alkalineesolution or .other :solvent, i: e., dioxane,ethylene glycol, .etc., ;to .giveiaipaste, or (3) theligninvmay'.be::mixed'with; aysufiicient quantity ofp fugitive?alkalifsuch asiammdnia; or, morpholine, or a polymerizable chemicalsuchgfas' aniline or aniline-furfural mixture, with 'Qsufiicientagitation ortrituration, or with other agents, as for 'example reactablechemicals (tolu'idine, cresol). Rubber plasticizers, e..g.diethylene-gly'e col, coal tar bases, capable of gelling-with lignin mayalso beemployedzfor this purpose .andaflige V nin gel formed inthef'same way; ii -es; triturae tion, agitatiom'etc; However formed,"the lignin gel as such, or mixedwithother pigmentgorplaaiticizer maybemilled with the rubber. alongswith other agents, e. "g.-,- other:reinforcingljagents; pigm-ents, accelerators, curing agentsgetci: .Luithis manner .the lignin or lignin-pigment. xmixturesis dispersedin therubber and the lignin subdivided into particle size to give .areinforcing .elfect com-' parable with that obtained by.cOpreeipitatiO'n with the rubber; Such action, however, istotbedistinguished from the use ofdried. precipitated lignin which isgenerally of large iparticleasize, about one to. five microns,- and doesnotigiwezreinforcing action which is comparable with-either carbonblackor coprecipitated lignin. .Whempoly merizable or-reactable chemicalshave been used .to gel the lignin, they will, under curing,:p oly+merize or react and-"to somelextent serve-as a reinforcing agent,and'filler for the rubberZ I-n the case-of a volatilizable' alkali; e.-.g;,'.=morpholine,

thisv will .be volatilized cduring,:thefcuringvand to'some extent duringthe milling. g 7 Since; the lignin is slightly acidid'in nature; itspresence retardssomewhat the cure wh'erelthe usual alkaline acceleratorchemicals such-"as dn phenyl guanidine or mercaptobenzothiaz'ole" areused. This may bereadily overcome by .the-ius'e of more or strongeraccelerator chemicals, such as copper diethyldithiocarb'amateor'.'=tetramethyl-' thiuram monosulfide, or bylincreas'ingstheamount ofabase present, as by increasingxthe quantity of the zinc oxide. Or,Itheiaciditymay be re= duced by adding alkalis, alkaline substancessuch.

as amines-,or. compounds ::of groups I; II, and III metals such as limewhichx form salts with lignin: 'These may be added '.either .whi'lemill= ing or preferably to the wet 'coprecipitatesof ligninandrubbene V.i Advantages -maybe otherwise taken3'of" the property of lignin of'beingsoluble mane gelling in alkalinesolutions lIlOIfdelltO form adisper sion'of it with rubber latex. i ,For example, -the lignin may beadded totheila'tex as a iwetslur-ry and athorough mixture obtained-byagitation. Where, as is usual, the pH ofzthe' latexiis on the alkalineside, the'lignin,:which has'ian acidfreaction, willdissolve and-cause adrop of'thapH t0;a point where the rubber'and lignin willipr cipitate.Furthermore, such of the r ligninf if any, as does notprecipitateiwillbe gelledun'der these conditions and in this 'form will"beread--' ilysubdivisible and dispersible inthe milling- 0p eration, as has alreadybeen pointed out. If-"nee essaryjthepH of'the m'ixture'm'aybe adjustedto the desired-point to completelyprecipitatethe rubber or the rubberand lignin mixture." I Eyen dry lignin when mixed with latex undertheseconditions will similarly become either dissolved or gelled. Otheralkalis than thealkali, metal hydroxides may be used tosolubilizethe'filig-nin', as for example ammonia, triethanolamine,'diethanolamine, -etc. i ,i -While acids are commonly used for'form ingthe lignin-latex coprecipitate, their coprecipitation can be induced byother means. Thus, a fugitive alkali such as ammonia, morpholine orpolymerizable, amines, e. g., aniline, may be used to solubilize thelignin; and then, after addition of the solution to the latex,coprecipitation maybe induced by heating. This effect may also be aidedby the addition of electrolytes. Coprecipitation may also be inducedbyeither freezing or evaporation. 1

, Additionally, the electrolytic decomposition of latex-lignindispersions or solutions is likewise practical.

.Lignin is generally identified as that component of Wood which, isinsoluble in 72% H2804; it is a compound of carbon, hydrogen and oxygen,and sometimes of the foregoing plussulfur, and is further characterizedby being soluble in solvents such as dioxane and by having sufficientacidity so that it will combine with sodium or nitrogen alkalis, andform water soluble compounds which can be precipitated by adding acids.In sulfite cooking the lignin of thewood is rendered soluble by theaction of the Wood with cooking liquors. These extractsof the woodeither as such or partly purified are sometimes mistakenly termedlignin" but are actually lignin sulfonates. It is possible to treatlignin sulfonates with alkali to convert them to a form which isinsolubl in water but soluble in alkaline solution, the same assulfateor soda lignin. When so treated, such sulfite lignin would come withinthe purview of my invention.

The lignin used in the foregoing examples was obtained by firstconcentrating the black liquor from the sulfate cooking of pine wood,removing tall oil skimmings, lowering the pH of the liquor by treatmentwith carbon dioxide gas, and coagulating the lignin by heat andpurifying by acid washing. The lignin so made is a ,dry'xpowder havingthe following range of analysis:

-Mois ture percent 4 Ash -1 d Less than 0.5 .Sulfur do l-2 Methoxyl do13.5-14.5 Dioxane insolubles 'do Less than 1 A still further source ofligninsuitable for the purpose of the present application is thesaccharification of the wood and other ligneous vegetable matter, e. g.,the Scholler process and its modifications, which produces an insolubleligneous residue which is highly acidic, containing some sugars,hemicelluloses and other degradation products of cellulose. Thismaterial is; susceptible to purification to yield a material suitablefor coprecipitation with rubber.

The product of this application is termed an elastomerby which is meanta composition having the ability to stretch, upon the application ofstress, from 200 to 300% or more of its original length, and afterrelease of the stress to return to essentially its original length. Thecurves, particularly Figs. 2, 8 and 12, illustrate this property. Ingeneral, it will be seen that throughout the loading up to 100 volumesthe elastomer produced conforms to this definition.

It is recognized, however, that for most rubber uses known today, theoptimum properties are not developed until quantities of reinforcingagent in excess of 10 volumes percent have been incorporated as can beseen from an examination of Figs. 1, 2, 3 and 3a.

. ln theclaims it will be understood thatrubber is intended to includeboth natural and synthetic rubberoriginally occurring as an aqueousalkaline emulsion unless the contrary is indicated. This application isa continuation in part of application Serial No. 603,748 filed July 7,1945.

I claim: i i I l.' The method of making an elastomer, which comprisesaddinglignin to alkaline latex of a polymeric-butadiene rubber therebycausing the coagulation of the rubber in the latex and the entrapment oftherubber in lignin gel, recovering the rubber and lignin gel,masticating and softening and effecting breakdownof the rubber andcausing the subdivision of the lignin gel and the dispersion thereof inthe rubber.

' 2, The method of producing coagulum of butadiene- LB-styrene copolymersynthetic rubber which comprises mixing aqueous sodium lignate withlatex of the rubber and then simultaneously coagulating the rubber andprecipitating lignin from the solution to produce coagulum of the rubberin which the precipitated'lignin is substantially uniformly dispersed.

3. The product produced by the method of claim 2.

4. The method of making a reinforced elastomer which comprises mixingaqueous alkali .lignate and a latex of a polymeric butadiene rubber,coprecipitating the rubber and lignin to produce a coagulum containingthe rubber and lignin, drying the coagulum, masticating and softeningand eifecting breakdown of the same thereby forming a reinforcedelastomer having the lignin substantially uniformly dispersed.therethrough, the lignin serving as a reinforcing agent.

.5. The product produced by the method of claim 4.

6. The method of claim 4; in which the rubber is natural rubber.

7. The product produced by the method of claim 6.

i s. The method ofclaim 4 in which the rubbe .is butadiene 1,3-styrenecopolymer. 1

9. The product of'the method of claim 8. 10. The method 'ofclaim 4 inwhich the rubber is butadiene 1,3-acrylonitrile copolymer. H

a 11. The product of the method of claim 10.

12; The method of claim 4 in which the is chlorobutadiene polymer.

13. The product of the method of claim 12.

14. The method of making a reinforced elastomer which comprisespreparing a substantially homogeneous mixture of lignin and a latex of apolymeric butadiene rubber, coprecipitating the rubber and lignin toproduce a coagulum containing the rubber and lignin, drying thecoagulum, masticating and softening and effecting breakdown of the samethereby forming a reinforced elastomer having the lignin substantiallyuniformly dispersed therethrough, the lignin serving as a reinforcingagent.

15. The reinforced elastomer produced by the method of claim 14.

16. The method of claim 14 in which the rubber is natural rubber.

1'7. The reinforced elastomer produced by the method of claim 16.

18. The method of claim 14 in which the rubber is butadiene 1,3-styrenecopolymer.

19. The reinforced elastomer produced by the method of claim 18.

20. The method of claim 14 in which the rubber is butadiene1,3-acrylonitrile copolymer.

rubber -copolymer of butadiene and styrene.

anemia? 21. The reinforced elastomer produced by the method of claim 20.a

, 22'. The method of claim' 14 in whichth rubber is chlorobutadienepolymer. 1

23J'Ihe reinforcedelastomer produced 'by the 1 method ofclaim 22. p I

24. The method of making a reinforced elas-' breakdown of th'samethereby forming a reinforced elastomer having the lignin substantiallyuniformly dispersed therethrough, the lignin serving as I a reinforcingagent. the parts of i-lignir'i basedon one hundred parts of polymerbeing from in excess of one to approximately one hundred,

reinforced elastomer produced by the method of claim 24.

26. The reinforced elastom'er produced by the method of claim 24 'inwhich the rubberis a 27. The reinforced elastomer produced'by the methodof claim 24 in "which the rubber is buta'diene acrylonitrile copclymer.

28. The reinforced elas'tomer produced by the method of claim 2';inwhich the rubber is chlo robu't'adiene polymer.

-29. Th reinforced elastomer produced by the method' of claim 24 m whichthe rubber is natural rubber.

30. The method of claim '24 -in which the rubber is'a copolymer ofbutadiene and styrene.

.31. The method of claim 24 in whichthe rubber isbutadiene-aerylonitrile copolymer.

32. l'he method of claim 24 in which the 'ubber is chlorobutadienepolymer.

33. The method of claim 24 in which the rubber is natural rubber.

34. The method of making an elastomer, which comprises first forming asuspension of rubber reinforcing pigment in a solution of lignin, mixingsaid suspensionwith a polymeric butadiene rubber latex, coprecipita'tingthe rubber, pigment andlign-in from said suspension to form a crumb, andhomogenizing the crumb with ad- 'ditio'rial lig'nin in' tneg'eu'edstate, together with a curing agent.

rubber-is chlorobutadiene.

7 V M m of claim 42.", V '44. The-method of making-a reinforced elas- 2-35. -A-productofthe -method or-eia'im' 34-. V 36. The me'thod' of claim34- inwhich the rubber isinatural -ru'bber.-- v k g 1 3'7."The productof the method o'f claim 36. 38. The method of claim 34 in which therubberis butadiene LB-styrene. Y. 39. The product'of the method'of claim38; 40. 'The method of claim 34 in which the rubberisbutadiene-1,3-acrylonitri1e. a I 41. The product of the method'ofclaim 40; -42. The method of claim 34 in which the 43. The product ofthe method with polymeric butadiene rubber. i 1 a 45. The product of themethod of claim 44.= '6. The method of claim :44 in Which-the polymer isnatural rubber.

47. Theproduct of the method of claim 46. '48. The {method of claim 44'in which the polymer is butadiene-lB-styrene 'polymer' -isbutadiene-1,3 styrene copolymer;

49. The productof the method of claim 48. .y 50. The method of claim 44'in which the polymer is butadiene-1,3-acrylonitrile;

'51-. The product of the method of claim 50.

52. The method of claim 44 in which the polymer is'chlorobutadiene. i

53. The product of the method of claim 52.

ARTHUR' Q L K.

REFERENCES CITED The following references are of recordin. the file ofthis patent: l I

tc'mer which comprises milling a 'gel of lignin Date 'Number Name 7 IUNITED STATES PATENTS f Number 7 Name Date- -1,833;029 Mac Kay Nov;i24,1931 2,195,380 Patrick Mar. "26:,'-19'40 2,343,363 Daly Mar. '7, 19442,353,568 King l July ll, 1944 2,355,180 De Remy Aug. 8, 1944 BascomAug. 7,;1945

v OTHER REFERENCES Indulin For Reinforcing .Rubber, published 1946 byIndustrial Chemical Sales DivisiomWest Va. Pulp and Paper Co., 31 pages.

4. THE METHOD OF MAKING A REINFORCED ELASTOMER WHICH COMPRISES MIXINGAQUEOUS ALKALI LIGNATE AND A LATEX OF A POLYMERIC BUTADIENE RUBBER,COPRECIPITATING THE RUBBER AND LIGNIN TO PRODUCE A COAGULUM CONTAININGTHE RUBBER AND LIGNIN, DRYING THE COAGULUM, MASTICATING AND SOFTENINGAND EFFECTING BREAKDOWN OF THE SAME THEREBY FORMING A REINFORCEDELASTOMER HAVING THE LIGNIN SUBSTANTIALLY UNIFORMLY DISPERSED